#include <stdlib.h>

void _Exit(int status);

#include <unistd.h>

void _exit(int status);


Partially implemented


IEEE Std 1003.1-2017


The _Exit() and _exit() functions terminate the calling process.

The value of status may be 0, EXIT_SUCCESS, EXIT_FAILURE, or any other value, though only the least significant 8 bits (that is, status & 0xff) are available from wait() and waitpid(); the full value is available from waitid() and in the siginfo_t passed to a signal handler for SIGCHLD.

The functions do not call functions registered with atexit() nor any registered signal handlers. Open streams are not flushed, but opened file descriptors are closed. Finally, the calling process is terminated with the consequences described below.

Consequences of Process Termination

All of the file descriptors, directory streams, conversion descriptors, and message catalog descriptors open in the calling process are closed.

If the parent process of the calling process has set the action for the SIGCHLD signal to SIG_IGN:

  • The process' status information, if any, is discarded.

  • The lifetime of the calling process ends immediately and a SIGCHLD signal is sent to the parent process.

  • If a thread in the parent process of the calling process is blocked in wait(), waitpid(), or waitid(), and the parent process has no remaining child processes in the set of waited-for children, the wait(), waitid(), or waitpid() function fails and sets errno to [ECHILD].


  • Status information is generated.

  • The calling process is transformed into a zombie process. Its status information is made available to the parent process until the process' lifetime ends.

  • The process' lifetime ends once its parent obtains the process' status information via a currently-blocked or future call to wait(), waitid() (without WNOWAIT), or waitpid().

  • If one or more threads in the parent process of the calling process is blocked in a call to wait(), waitid(), or waitpid() awaiting termination of the process, one (or, if any are calling waitid() with WNOWAIT, possibly more) of these threads obtains the process' status information as specified in Status Information and becomes unblocked.

  • A SIGCHLD is sent to the parent process.

Termination of a process does not directly terminate its children. The sending of a SIGHUP signal as described below indirectly terminates children in some circumstances.

If the process is a controlling process, the SIGHUP signal is sent to each process in the foreground process group of the controlling terminal belonging to the calling process.

If the process is a controlling process, the controlling terminal associated with the session is disassociated from the session, allowing it to be acquired by a new controlling process.

The parent process ID of all of the existing child processes and zombie processes of the calling process are set to the process ID of an init system process. That is, these processes are inherited by a init process.

Memory mappings that were created in the process are unmapped before the process is destroyed.

Threads terminated by a call to _Exit() do not invoke their cancellation cleanup handlers or per-thread data destructors.

If the calling process is a trace controller process, any trace streams that were created by the calling process are shut down as described by the posix_trace_shutdown() function, and mapping of trace event names to trace event type identifiers of any process built for these trace streams may be deallocated.

Return value

The functions can never return.


No errors are defined.


See Also

  1. Standard library functions
  2. Table of Contents